Summer Jam concert erupts into chaos as agitated crowds try to get in

A hip-hop and R&B concert in New Jersey erupted into chaos Sunday night when police in riot gear tried to contain agitated crowds.

By Faith Karimi and Laura Ly CNN

(CNN) -- A hip-hop and R&B concert in New Jersey erupted into chaos Sunday night when police in riot gear tried to contain agitated crowds.

The melee started when attendees tried to forcefully enter the Summer Jam concert at MetLife Stadium in East Rutherford, authorities said.

"Security personnel at one of the entrance gates ... were confronted by crowds attempting to illegally enter the sold out Summer Jam concert by climbing over fences and forcing their way through security personnel," New Jersey State Police said.

Troopers on site asked for extra backup to help maintain order, Sgt. Gregory Williams said. Witnesses said authorities arrived in riot gear.

"We have the riot gear all the time and we were ready in case something was to happen and we had to use it," he said.

But some witnesses provided a different account.

Jerry Arnold, who was at the concert but did not get in, said attendees got upset because it was taking too long to go through security.

"Security was being extremely slow, and people were waiting to be let in," he said. "I had a ticket. Everyone had ticket, but security was being very slow and everyone got agitated."

Officers with shields used mace to disperse the crowd, causing more chaos and delaying the concert by hours, according to witnesses.

"People were falling down, trampling onto each other," Arnold said. "The concert started at 6 p.m. and at 9 p.m., people still weren't getting in."